Preliminary endocrinological evaluation of a sustained-release formulation of the LH-releasing hormone agonist D-Ser(But)6Azgly10LHRH in premenopausal women with advanced breast cancer.

Twenty-four premenopausal women with advanced breast cancer were treated with a sustained-release (depot) formulation containing 3.6 mg of the LH-releasing hormone agonist D-Ser(But)6Azgly10 LHRH (ICI 118630), given s.c. every 4 weeks for periods of up to 5 months. Although ICI 118630 initially stimulated LH and FSH secretion, serum gonadotrophin concentrations were suppressed on continued treatment. Increased LH and FSH concentrations were associated with relatively normal ovarian activity during the first month of treatment, but low progesterone concentrations were found in all patients thereafter. In 22 out of 24 women, oestradiol concentrations fell during the second month to values equivalent to those observed in oophorectomized or postmenopausal women. In two patients, persistent but reduced oestradiol production was recorded throughout. No appreciable side-effect of the drug was observed.